docs: def _compute_mean(self, C, mag, ztor, rrup):
          """
          Compute mean value as in ``subroutine getGeom`` in ``hazgridXnga2.f``
          """
          gc0 = 0.2418
          ci = 0.3846
          gch = 0.00607
          g4 = 1.7818
          ge = 0.554
          gm = 1.414
  
          mean = (
              gc0 + ci + ztor * gch + C['gc1'] +
              gm * mag + C['gc2'] * (10 - mag) ** 3 +
              C['gc3'] * np.log(rrup + g4 * np.exp(ge * mag))
          )
  
          return mean